It may be about the time you've forgotten about one of part of your New Year's resolutions: The part about eating healthy, exercising more and encouraging friends, loved ones and co-workers to do the same.

Thanks to a study to be released today in the Journal of the American Medical Association, we have a study that not only bolsters evidence you can't be fat and healthy at the same time, but spells out middle-age people are simply kidding themselves of they are overweight and have normal blood pressure and cholesterol levels, and try to believe their health is just fine.

Northwestern University researchers tracked 17,643 patients for 30 years and discovered being overweight in mid-life substantially increased the risk of dying of heart disease later in life - even in people who began the study with healthy blood pressure and cholesterol levels.

High blood pressure and cholesterol are strong risk factors for heart disease. Both are common in people who are too fat, and often are thought to explain why overweight people are more prone to heart disease.

However, a growing body of science suggests excess weight alone is an independent risk factor for heart attacks, strokes and diabetes.

The new study fits with that evolving school of thought and contrasts with a controversial government study published last year that suggested excess weight might not be as deadly as previously thought.

Participants were Chicago-area men and women in their mid-40s on average who had no heart disease or diabetes when the study began. They were followed for an average of 32 years. The researchers tracked deaths from cardiovascular disease and diabetes, and hospitalizations for those conditions, starting at age 65.

A total of 1,594 heart disease deaths occurred, 31 of them in people who started the study with normal blood pressure and cholesterol.

Among participants with normal blood pressure and cholesterol at the start, those who were obese or grossly overweight were 43 percent more likely than normal-weight participants to die of heart disease later in life. They were also four times as likely to be hospitalized for heart disease.

Participants who were modestly overweight but had normal blood pressure and cholesterol still ran a higher risk than the normal-weight people.

A total of 1,187 participants - 494 of them overweight or obese - had normal blood pressure (120 over 80 or lower) and cholesterol levels (under 200) at the outset. Standard body-mass index categories were used to define weight - BMIs of 25 to 29 were considered overweight and 30 and above was obese.

The common misconception that excess weight is nothing to worry about until high blood pressure and poor cholesterol develop, and then be treated with medications, was answered by study authors:

Pay more attention to your weight, even if you don't have an unhealthy risk factor profile yet, they said.

The study "will help define obesity as a disease" in itself, said Dr. Samuel Klein, an obesity expert at Washington University in St. Louis.

Dr. David Katz, an obesity researcher and director of Yale University's Prevention Research Center, said the findings help prove obesity is a real public health crisis. "People who say obesity has been hyped are wrong," Katz said.